My car set in my garage for a year not driving.

My car set in my garage for a year not driving it. Car would not start so replaced the battery, still would not start, had it towed to a mechanic, after everything was checked, car still did not start, mechanic said problem might be in the computer, he found a part at a junk yard or somewhere and the car started but now the turn signals do not work but I am sure they worked before, lights and everything else works okay in the car, I took the car back to the mechanic, checked fuses which were okay, o whar do I do now